As it is known, to optimise the combustion process in cylinder(s) in an internal combustion engine it is necessary to maintain the air-fuel ratio in each cylinder, as much as possible, in proximity to the stoichiometric value.
The devices and methods currently utilized and available in the market for measuring said air-fuel ratio are based on oxygen sensors, usually housed in the outlet conduit in proximity to the catalytic converter. However, these sensors present certain drawbacks. These sensors, for example, are subject to breakage and are not able to effectuate measurements in each engine cylinder.